The flight was on its way to Sacramento when a 5 foot hole opened up in the roof, forcing the pilot to make an emergency landing in Arizona.
ABC News has learned part of the problem may have been a defect when the plane was manufactured in 1996.
Investigators say rivets that hold pieces of the airplane together - were not held as tightly together as they should have been.
Boeing ordered inspections of similar planes around the world after the incident. Only five planes, so far, have slight cracks.